Calculate the luminosity of the star with an apparent magnitude of 2. Given the Sun has an apparent magnitude of -26.57 and 3.9 × 1026 W luminosity.

Betelgeuse is a nearby supergiant that will eventually explode into a supernova. Let's see how awesome it would look. At peak brightness, the supernova will have a luminosity of about 10 billion times the Sun. It is 600 light-years away. All stellar brightnesses are compared with Vega, which has an intrinsic luminosity of about 60 times the Sun, a distance of 25 light-years, an absolute magnitude of 0.6 and an apparent magnitude of 0 (by definition). a) At peak brightness, how many times brighter will Betelgeuse be than Vega? b) Approximately what apparent magnitude does this correspond to? c) The Sun is about -26.5 apparent magnitude. What fraction of the Sun's brightness will Betelgeuse be?

Two stars-A and B, of luminosities 0.5 and 4.5 times the observed to have the luminosity of the Sun, respectively-are same apparent brightness. Which star is more distant, and how much farther away is it than the other?

A red giant star has a temperature of 3900  K and a luminosity of 13600 LSun. How many times bigger is this star than the Sun? Hint: You need the surface temperature of the sun for this problem. Use the value in the book, 5800K.